1. Field of the Invention
The present invention relates to a thermal transfer recording method. Further, the present invention relates to an apparatus for carrying out the aforesaid method.
2. Description of the Prior Art
In the hitherto known facsimile apparatus, as means for receiving image information of an original and recording it, the electrostatic recording method and thermal transfer recording method are mainly employed for the signal receiving and recording mechanism. The electrostatic recording method has an advantageous feature that recording can be effected at a high speed with high image resolvability, but it has drawbacks that the apparatus using this method is complicated and expensive because developing and fixing of images are required. In addition, recording paper used in this apparatus is expensive, resulting in comparatively increased running cost. On the other hand, the thermal transfer recording method has advantageous features that developing and fixing of images are not required because the image is built by primary coloring under the effect of heating and an apparatus using this method can be constructed in a comparatively simple manner, but it has drawbacks that recording papers are of specially produced type which have less durability and the images recorded thereon can be falsified relatively easily.
In view of the problems inherent to the recording methods as described above, it has been proposed that thermal transfer recording apparatus be used for facsimile equipment in which inexpensive ordinary paper is employed as recording medium. The thermal transfer recording apparatus of this type is operated such that recording paper, made of ordinary paper; and ink ribbon, serving as master recording material and comprising a base film made of paper, plastic or like material with a layer of thermally fusible solid ink containing coloring agent coated thereon; are superimposed one above another so that the ink layer comes in contact with the recording paper and they are transported in a certain direction while the base film is depressed by means of a platen roller so as to allow it to come in contact with heating resistor elements of a thermal head. When pulse electric current is selectively caused to flow through the heating resistor elements in response to signals representing an image to be recorded, heat is generated at the heating resistor elements. The generated heat is transmitted to the solid ink layer through the base film of the ink ribbon. Thus, the solid ink layer becomes viscous and is in a semi-fused state. The semi-fused ink is transferred to recording paper under the influence of pressure provided by the platen roller whereby a permanent image is transferred to the paper.
Since this type of recording apparatus uses ordinary paper as the recording medium and does not require processes of developing and fixing, running cost can be reduced considerably and the apparatus can be manufactured in a simple construction, in smaller dimensions and at an inexpensive cost. Further, since coloring agent having excellent weather resistance is used for the ink which is transferred only onto a required area on the paper, the recording paper and the recorded images are durable for a longer time and falsification of the recorded image is difficult compared with the foregoing heat sensitive recording apparatus.
However, it has been pointed out that the existent thermal transfer recording apparatuses fail to satisfactorily meet a variety of requirements for receiving and recording image signals when used in a facsimile apparatus.
For instance, when the thermal transfer recording apparatus of the above type is applied to a facsimile apparatus, recording paper having the size of A4 (29.7 cm.times.21 cm) or B4 (36.4 cm.times.25.7 cm) is used as recording medium and therefore the length of an original of which image signals can be completely sent and received is limited by the length of the sheets of recording paper. Further, in the conventional thermal transfer recording apparatus, the ink ribbon and the recording paper correspond to each other in the one-to-one relation and the length of ink ribbon is determined to have the length of the recording paper. Therefore, both the ink ribbon and the recording paper tend to have a blank area which is not concerned with recording operation. This is not preferable from the view point of cost and process efficiency. Further, since the paper storage section for storing a pile of paper sheets require a considerably large space, the thermal transfer recording apparatus using ordinary paper is more difficult to use in a small facsimile apparatus designed to be placed on a desk than in the case of the hitherto known heat sensitive recording apparatus.
Furthermore, the conventional thermal transfer recording system uses an ink ribbon made of very thin film having a thickness of about 10 micrometers and, therefore, very careful handling is required during the whole operation of the facsimile apparatus. In view of the fact that the ink ribbon and the recording paper are transported while they are superposed one above the other, there is a fear of causing deterioration of the recorded image. In the extreme case it becomes impossible to effect recording due to a number of wrinkle lines over the whole length of ink ribbon which tend to be developed during production of ink ribbon or when the facsimile apparatus is operated incorrectly.